A typical pipeline valve is equipped with one or more flanges. The purpose of the flanges is to allow the connection of the valve to another flanged valve, to a flanged pipe or to a flanged fitting. To enable the flange of the valve to be attached to the mating valve of the applications described above, the bolt holes on the mating flanges must be geometrically aligned.
In valve designs where it is necessary to attach the valve flange to a valve body by means of a screw thread, it is not always possible to ensure that the valve flange can be fastened to the valve body such that the bolt holes of the valve flange are in the correct geometrical alignment. It is normal to apply torque to the valve flange such that an axial loading is applied through the mating threads in order to prevent the threaded connection from becoming loose. However, when the valve flange is screwed on tight to the valve body, the bolt holes of the valve flange may not be correctly aligned.
One existing approach to the problem is to incorporate a disc type spring such that as the mating threads are screwed together, the disc spring is compressed and this provides the axial loading on the mating threads while allowing a limited rotation of the mating threaded connection in order to bring the valve flange bolt holes into the correct alignment.
Another approach to this problem is to design a deformable feature into either the valve flange or the valve body such that as the valve flange is screwed into the valve body, where the deformable feature imparts an axial loading to the mating threaded connection while allowing a limited amount of rotation of the mating threaded connection in order to bring the valve flange bolt holes into the correct alignment.
In both of the previously described approaches, axial loading is applied to the mating threads when the spring or deformable feature comes into effect. Therefore, the axial loading applied to the mating threads is affected by the need to achieve geometrical alignment of the valve flange bolt holes. Further, the resistance to rotation of the valve flange relative to the valve body is determined by the frictional resistance of the mating faces and the mating threads.
What is needed is an apparatus for applying an axial load to the mated threaded connection of a valve flange and valve body whilst permitting geometrical alignment of the bolt holes in the valve flange and providing non-frictional resistance to rotation, that overcomes the problems in the existing art.